Conventionally, with respect to partially-oxidizing methods for hydrocarbon, processes for directly manufacturing an epoxide by partially oxidizing a hydrocarbon of the olefin family have been carried out; however, in most of these processes, oxidizers, such as hydrogen peroxide, organic peracids, and chlorine compounds, are used.
In contrast, processes for transforming hydrocarbons into oxygen-containing compounds by using oxygen, such as, for example, processes for directly manufacturing epoxides from hydrocarbons of the olefin family through a partially-oxidizing reaction using oxygen, have been considered as a very prospective technique since oxygen, which is inexpensive as compared with the above-mentioned oxidizers, is used.
However, it is generally considered to be difficult to directly obtain an alcohol and a ketone that are useful compounds from a saturated hydrocarbon and also to directly obtain an epoxide from an unsaturated hydrocarbon except for rare exceptions, and these practices have hardly been carried out except for a manufacturing method for ethylene oxide.
In particular, with respect to methods for manufacturing propylene oxide by oxygen-oxidizing propylene and catalysts used therein, many suggestions have been made; however, none of these methods have been successfully put into practice since conventional commonly-used catalysts raise problems in performances such as low selectivity.
In order to solve these problems, direct-oxidizing methods, etc., such as the chlorohydrin method, the HALCON method, and the acetyl-hydroperoxide method, have generally been used as the methods for manufacturing propylene oxide by oxygen-oxidizing propylene. However, these manufacturing methods raise other problems in which two reaction processes (two stages) are required and by-products (additional produces) are produced.
For this reason, simpler, more effective manufacturing methods have been demanded, and various methods for manufacturing propylene oxide by directly oxygen-oxidizing (partially oxidizing) propylene that is a hydrocarbon of the olefin family and catalysts used for the manufacturing methods have been proposed.
For example, Japanese Laid-Open Patent Publication No. 97378/1995 (Tokukaihei 7-97378) discloses a method for manufacturing olefin oxide (an epoxide) from olefin (an unsaturated hydrocarbon) in a gaseous phase by using as a catalyst crystalline silicate (silicate) on which metallic salt of nitric acid, such as silver nitrate, is deposited.
Further, Japanese Laid-Open Patent Publication No. 352771/1992 (Tokukaihei 4-352771) discloses a method for manufacturing propylene oxide from propylene in a liquid phase by using a catalyst made of a metal of the VIII family and crystalline titano-silicate.
However, since the catalysts used in these manufacturing methods are inferior in catalyst performances such as activity and selectivity, it has to be said that the above-mentioned conventional methods fail to provide practical manufacturing methods for epoxides.
For this reason, inventors and other personnel of the present application have earnestly made research into a partially-oxidizing method for a hydrocarbon by which an alcohol and/or a ketone can be obtained from a saturated hydrocarbon and an epoxide can be obtained from an unsaturated hydrocarbon, by partially oxidizing the hydrocarbon in the presence of oxygen and hydrogen, and a catalyst that is preferably used for the above-mentioned partially-oxidizing method for hydrocarbon. Consequently, it has been discovered that a catalyst containing gold and titanium oxide is preferably used for the partially-oxidizing method for hydrocarbon.
Accordingly, in Japanese Laid-Open Patent Publication No. 127550/1996 (Tokukaihei 8-127550), the inventors and other personnel of the present application have disclosed a method for manufacturing an epoxide by oxygen-oxidizing an unsaturated hydrocarbon in the presence of molecular hydrogen and a catalyst containing gold and titanium oxide. With this method, it is possible to obtain epoxides with high selectivity.
However, the above-mentioned catalyst, provided by the inventors and other personnel of the present application, is found to be inferior in the activity although it has high selectivity. For this reason, in the case when, for example, the catalyst is applied to a manufacturing method for an epoxide, the conversion of the unsaturated hydrocarbon to the epoxide is as low as not more than 3%, and the amount of hydrogen to be burned is high.
In the reaction using the above-mentioned gold-titania catalyst, there is a tendency in which although the consumption of hydrogen is increased by increasing the reaction temperature (especially, at not less than 100.degree. C.), it is difficult to increase the product activity of the partially-oxidized product, such as an epoxide, and the amount of product of the partially-oxidized product does not increase or reduces. In other words, in the above-mentioned catalyst, the maximum level of the catalyst performance, which is achieved by optimizing the reaction conditions such as reaction temperature, is comparatively low, and further improvements are required to put the above-mentioned reaction into practical use.
The first objective of the present invention that has been devised to solve the above-mentioned problems is to provide a partially-oxidizing catalyst for hydrocarbon which has superior activity and selectivity in carrying out a reaction for partially oxidizing the hydrocarbon in the presence of hydrogen and oxygen and which can make the partially-oxidizing reaction put into practical use with high selectivity and high conversion.
Moreover, the second objective of the present invention is to provide a partially-oxidizing method for hydrocarbon which allows to obtain an epoxides from a hydrocarbon of the olefin family (an unsaturated hydrocarbon) and also to obtain an alcohol and/or a ketone from a saturated hydrocarbon, with high selectivity and high conversion.